Simple Solutions That Work! Issue 18

the liquid metal in the full mold results in highest accuracy of the subsequent modeling of cooling and solidification of the metal. Figure 3 shows the prediction of a misrun in a copper-base casting that was poured too cold. Figure 4 shows that filling can be completed by increasing the pouring temperature. Another aspect of filling simulation which is quite useful is prediction of metal velocity during filling. Areas of higher velocity are also areas where excessive turbulence is likely, leading to formation of dross (oxides) as the turbulence entrains oxygen-containing gas into the metal stream. Of course, this effect does depend somewhat on the affinity of the particular alloy for oxygen, so this is more important in alloys such as aluminum which has a great tendency to oxidize as opposed to a carbon steel which has a relatively low affinity for oxygen. Almost all alloys, however, have some tendency to form oxides and using flow simulation to design gating systems which minimise velocity and turbulence of the metal can be quite helpful in reducing flow-related defects in castings. Figure 3. Plot of a misrun predicted by CFD fluid flow simulation. Figure4. Complete mold filling with an increase in pouring temperature. Contact: DAVID C. SCHMIDT [email protected] 46